Re-assert cloudformation control of ECR registry definitions (for cross account permission purposes)

- Our ECR repos were created with CF
- During a re-factor, sceptre tried to delete them but they cannot be deleted since they are in use
- Ashley knows a technique to fix this
- When time permits, Terry and Ashley should meet to resolve this.

## What needs to be added?

For the prod account, add permissions
```
ecr:ListImages, ecr:DescribeImages, ecr:PutImage
```